The purpose of this experiment was to see whether innocent people would conform to the labels given to them within the prison system.
A police car picked up college students who had volunteered to take part in an experiment. The students didn't know this would happen. They were arrested and blind folded before being taken to the 'prison' the was built in the basement of Stanford University.
Each prisoner was systematically searched and stripped naked once inside the prison. They were then deloused with a spray to convey our belief that they may have germs or lice. They were then given a uniform and ID number.
The aim with fake prison was to make the same feelings that real inmates would feel while incarcerated. The use of the ID numbers was to make the prisoners feel anonymous.
The guards in the prison were also volunteers and were given no training before entering the prison as guards.
During the day the guards would make the prisoners do a variety of things to assert their authority over the prisoners and the prisoner's let them, conforming to the labels of prisoner and guard like Zimbardo thought would happen.